Landlord in Vermont Raising Rent Unexpectedly - What are my options?

Hi there r/legaladvice. I'm currently renting in Vermont. When signing my original lease with my landlord, we (my current roommates and I) informed him that we'd be adding a roommate at the end of August. He said this was fine. My incoming roommate is not on the current lease.

When we reminded our landlord this week that he'd be moving in at the end of this month, he suddenly sprang an extra $250/month for adding another person. This was never mentioned when signing the lease. I'm not looking to complain, just wondering what my options are? Is there any way I can fight this, or do I have to just go along with it since we may have to sign a new lease with the new roommate's signature on it?

I can clarify any details I may have missed, just want to get this posted ASAP so I can deal with it in a timely manner.